Re: Too many poll_idle cpu calls in kernel 3.2 rc-series

From: Deepthi Dharwar
Date: Tue Nov 29 2011 - 06:07:17 EST


On 11/29/2011 02:14 AM, Andi Kleen wrote:

> On Mon, Nov 28, 2011 at 09:31:13PM +0100, Nicolas Kalkhof wrote:
>> Andi,
>>
>> correct. The issue was introduced somewhere between 3.1 final and 3.2-rc1. I've tried to track down the bad commit but so far I haven't been successfull. The only workaround I found is to set the idle boot parameter to mwait and to disable CONFIG_INTEL_IDLE. Somehow the kernel seems to set idle to poll by default - no idea why :-(. I wonder if other mobile sandy bridge cpus are affected as well.
>
> There are only a few changesets affecting drivers/idle
>
> Can you try to git revert
>
> 46bcfad7a819bd17ac4e831b04405152d59784ab
> 4202735e8ab6ecfb0381631a0d0b58fefe0bd4e2
> e978aa7d7d57d04eb5f88a7507c4fb98577def77
>
> ?
>
> -Andi


Hi,

I am guessing that for workaround just setting the idle boot parameter
to mwait should work. Have u tested this without disabling
CONFIG_INTEL_IDLE ?

Also one thing to note from your logs is, cpu is not entering any of the
other C states except for POLL. Can you also check if your are enabling
only POLL for idle. I am able to enter deeper C-states on i5-2540M with
Intel_Idle enabled.

Power top o/p:
-------------

Core | CPU 0 CPU 1
POLL 0.0% | POLL 0.0% 0.0 ms 0.0% 0.0 ms
C1-SNB 1.4% | C1-SNB 2.2% 0.7 ms 0.5% 0.9 ms
C3-SNB 0.9% | C3-SNB 1.6% 1.2 ms 0.1% 1.2 ms
C6-SNB 0.2% | C6-SNB 0.3% 1.6 ms 0.0% 0.9 ms
C7-SNB 95.8% | C7-SNB 93.7% 3.7 ms 97.8% 15.1 ms


Regards,
Deepthi

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